Phosphatase of Regenerating Liver (PRL) proteins have recently been touted as biomarkers that signify the ability of cancers to metastasize. However, the mechanism(s) by which PRLs contribute to cancer progression are unclear and importantly, contradictory cellular responses to PRL expression have been reported in mammalian systems. We plan to examine the function of PRLs using Drosophila melanogaster, which has proven to be a valuable model organism for cancer biology research. D. melanogaster encode only one PRL (dPRL-1), likely the ancestral gene to the three in mammals. Elevated expression of dPRL-1 suppresses cell proliferation and results in abnormal cell differentiation. One specific aim involves performing two genetics screens based on the growth inhibitory phenotype of dPRL-1 in order to identify regulators and effectors of dPRL-1 function. One screen will test candidate genes compiled from both mammalian and Drosophila studies while the other is an unbiased screen to allow the detection of novel genes that interact with dPRL-1. The results obtained from these screens will allow us to begin to construct a dPRL-1 signaling pathway. Because multiple subcellular localizations have been reported for mammalian PRLs, our second aim is to determine whether subcellular distribution of dPRL-1 modifies its function. We will develop an antibody to track when and where dPRL-1 protein is normally expressed during Drosophila development as well as its specific location within a cell. This will allow us to associate the subcellular distribution of dPRL-1 with developmental events. We will also genetically modified dPRL-1 in an attempt to override its normal distribution so that we can definitively determine whether subcellular localization regulates dPRL-1 function. We hope that our data will allow us to create a defined system (by manipulating the genetic environment and/or subcellular distribution of dPRL-1) that will enable dPRL-1 to behave like an oncogene. A more complete understanding of PRLs will allow clinical applications using these proteins as metastatic biomarkers to be better informed and thus, more effective. PUBLIC HEALTH RELEVANCE: Phosphatase of Regenerating Liver (PRL) proteins are promising biomarkers to assess the metastatic potential of cancers and could also serve as molecular targets to eliminate cancer cells. Thorough characterization of PRLs is paramount to understanding under what circumstances PRLs can contribute to cancers and is also necessary to assess whether targeting PRLs in cancers may harm healthy tissues as well.